A wealthy company president hires Kogoro after hearing one of his daughters is going to attempt to kill him, but when he is killed with video evidence, Conan and Kogoro must decipher the clues as to whom the real killer is.
The kille was doctor Okano. In the past, Ichikawa ruined his family by making his father (who also was his business partner) go into bankruptcy, sending him into a spiral of drunkness and depression that finished when the elder Okano killed himself few after his ill wife died, when their son was about to enter college.
Okano could have killed Ichikawa in any moment, as his personal doctor. However, he kept his feelings aside, and only decided to kill his boss when he confided in him and said that he planed to test Kazue and Mizue's love for him, via feigning a heart attack and analyzing the ladies's reactions. Instead of following his boss's instructions, Okano used the "test" to kill thim: Kazue did intent to kill Ichikawa via poisoned wine, Okano took advantage to give him a fatal medicine overdose.
